The spacing insulators can be used for installing different fuse sockets, rails, distribution- and switching electric boxes, furthermore other indoor electric devices within the rated voltage range. They are lighter than porcelain insulators and require less space. The spacing insulators are made by moulding from a proper mix of halogen free epoxy-resin and quartz-flour. The fixing metal inserts with thread are installed during moulding into the plastic body. They have good mechanical, thermal and electric quality. The installation is fast and precise with them. When it is necessary the dielectric strength can be increased by superposition of several spacing insulators.